In particular situations people may encounter harmful concentrations of hazardous chemicals. In such situations, it is necessary to wear chemical protective garments of special composition and construction. These protective garments are necessary for providing an effective barrier between the wearer and the chemicals encountered. However, as pointed out in U.S. Pat. No. 4,855,178 (Langley), in addition to providing an effective chemical barrier, materials for chemical protective garments should meet practical requirements for amenability to fabrication by existing methods (e.g., heat bonding of seams) as well as for providing sufficient strength to prevent tearing and the resulting loss of protection.
General practice in the protective garment trade is to construct chemical protective garments by seaming together panels of chemical protective garment material. These seams may be formed in a number of ways. The seams may be formed by traditional methods of sewing and then covering the seam with a layer of heat sealing tape. Alternatively, the seams may be formed by heat or ultrasonic welding of the garment material. These seams may utilize adhesives.
Suitable chemical protective garment materials must be flexible to allow manipulation during seaming on standard seaming equipment, whether it be by sewing, adhesives or heat sealing. The chemical protective garment materials must also be of a composition that allows the formation of strong sealed seams, whether these seams are sewn and taped, adhesively joined or whether they are welded by heat or ultrasonic energy.
In addition, chemical protective garments must be durable in use. The garments must not develop structural failures during use which would expose the wearer to hazardous chemicals. Thus, the chemical protective garment materials and the seams created in constructing the garments must be strong and resistant to structural failure (e.g., to tearing, cracking or shrinking).
In many situations, it is not feasible to decontaminate chemical protective garments after exposure to hazardous chemicals. A chemical protective garment contaminated with a hazardous chemical is generally considered as hazardous waste. There is limited space for the storage and burial of hazardous wastes. Chemical protective garments intended for limited-use, should be light in weight to reduce the burden on storage and disposal.
Strong, lightweight chemical protective garment materials made from laminates of different materials are known. U.S. Pat. No. 4,272,851 (Goldstein) describes a film of polyethylene that may be laminated to nonwoven chemical protective apparel. U.S. Pat. No. 4,772,510 (Mc Clure) describes a chemical barrier film laminated to a nonwoven substrate using an adhesive. Other laminates having multiple barrier layers are described in U.S. Pat. Nos. 4,855,178 (Langley); 4,833,010 (Langley) and U.S. Pat. No. 5,035,941 (Blackburn).
Often, each layer of a chemical protective garment material is chosen to impart a specific property to the composite fabric. Some layers provide strength while other layers may be chosen to provide permeation resistance against specific classes of chemicals. Additional layers add weight and stiffness. However, stiff garments are difficult to assemble and reduce the wearer's mobility.
There has been a general trend in the protective garment art to add additional layers to chemical protective garment materials to increase and broaden resistance to various classes of chemicals. This adds weight, stiffness and cost to these materials. For example, EP-0 434 572 (Boyer et al.) discloses a six (6) layered chemical protective garment material employing polyvinylidene chloride coated polyethylene terephthalate (PET) as the chemical barrier layer. The material comprises a nonwoven substrate, a layer of polyethylene, an adhesive layer, a layer of polyvinylidene chloride coated PET film, another layer of adhesive, and finally a layer of polyethylene. U.S. Pat. No. 4,920,575 (Bartasis) discloses a multi-layered structure that may contain one or two layers of a polyester film.
U.S. Pat. No. 4,214,321 (Nuwayser) describes a chemical permeation resistant, multilayer sheet material consisting of an outer abrasion resistant polymer resin, such as polyester or fluorocarbon, an intermediate layer of aluminum foil which does not allow the passage of organic solvents, and an inner heat sealable polymeric layer of polypropylene or polyethylene. What he does not describe, and which is well known among those conversant in the art, is that there must be at least one additional layer between the outer polymeric layer and the foil and at least one additional layer between the foil and inner heat sealable resin layer to adhere these layers into a single structure. Neither does Nuwayser recognize that an outer polyester layer, such as "MYLAR" polyester film, made by DuPont, provides a sufficient barrier to organic solvent permeation as was later disclosed in the "Journal of Plastic Film & Sheeting", Vol 6, page 106, April, 1990 (Goyden, et al).
Clearly, what is needed is a lightweight, chemical protective garment material, having a limited number of distinct layers, which can be assembled into a protective garment wherein the particular layers impart more than one property to the composite material. In particular, the applicants have recognized the need for a chemical protective garment material having a single barrier layer which provides protection against several classes of chemicals, which contributes to garment strength, and which provides for the construction of protective garments with strong seams. In addition, the applicants recognize a need for chemical protective garment materials that have a distinctive color. In addition, the applicants recognize the need for simplified processes to make such chemical protective garment materials.
An object of this invention is to make a new, improved chemical protective garment material from a thin film and a flexible woven or nonwoven substrate. This requires the right combination of ingredients and structure that give a composite material with the desired properties. It requires a barrier film that resists permeation to a wide variety of organic and inorganic chemicals. The permeation resistance of the barrier film must not be degraded by flexing. The barrier film should be lightweight so that it is flexible and economic to use, to dispose of after use and not increase the weight burden to user. The composite barrier material, with or without the flexible substrate should be strong in tensile properties and burst strength, and must allow the formation of strong, sealed seams and must resist tear propagation.
Another object is a composite material which does not create excessive noise or is stiff when fabricated into a garment; or the wearer can be hindered or perhaps endangered while doing his job. The layers in such materials must be strongly adhered, such that they do not separate when the material is flexed and crimped, or else the composite material looses properties dependent on the synergy of characteristics of the individual components. The composite should have adequate tear resistance to be practical when fabricated into chemical resistant clothing.
Other objects and advantages of the present invention will become apparent to those skilled in the art upon reference to the attached drawings and to the detailed description of the invention which hereinafter follows.